Tire carrier disk clutch with positive clip retention

ABSTRACT

A torque limiting clutch includes a drive shaft having central rotational axis and a groove, a spring member secured to the drive shaft for rotation with the drive shaft about the central rotational axis, a plate adjacent the spring member and rotatable about the drive shaft, and a retaining clip located within the groove of the drive shaft and engaging the plate to retain the plate on the drive shaft. The plate has a pocket forming an axial-facing first abutment engaging the retaining clip and a radial-facing second abutment located outward of the retaining clip to prevent release of the retaining clip from the groove.

CROSS-REFERENCE TO RELATED APPLICATIONS

Not Applicable

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH

Not Applicable

REFERENCE TO MICROFICHE APPENDIX

Not Applicable

FIELD OF THE INVENTION

The present invention generally relates to a torque-limiting disk clutchand, more particularly, relates to a disk clutch for a tire carrier of amotor vehicle.

BACKGROUND OF THE INVENTION

Motor vehicles with inflatable tires such as cars, vans, sport utilityvehicles, cross over vehicles, light and heavy duty trucks, tractortrailers, buses, commercial delivery vehicles, among other motorizedforms of motorized transportation and trailers pulled by such vehicleare conventionally equipped with spare tires. Some spare tires arestored under the vehicle using a tire carrier which includes a tirewinch for raising and lowering the spare tire between a raised or storedposition and a lowered or accessed position. The winch typically raisesand lowers the spare tire using a flexible member such as a cable orcord which is wound and unwound on a lift drum or reel.

Such tire carriers have been subject to failure due to over loading.When the winch is used to raise a tire from the lowered position to theraised position, the user is unable to determine when the tire isproperly stored in the raised position. Thus, in order to make sure thetire is properly raised, there is a tendency for the user to continue toexert torque on the lift drum in an attempt to further wind the cableabout the drum. This exerts ever-increasing tension on the cable and maycause it to break, resulting in failure of the tire carrier and the tiredropping to the ground.

Torque limiting clutches have been used to prevent rotation of the liftdrum once a predetermined maximum stress has been placed on the cable.After the maximum stress has been reached, application of additionaltorque results in the clutch overrunning to prevent additional tensionfrom being placed on the cable. Disk-type clutches have been found to bevery advantageous due to the resulting reduced package size. However,while such disk clutches effectively reduce the number of tire carrierfailures and provide a reduced package size, the prior clutches haveretaining clips that sporadically fall off. Accordingly, there is a needin the art for an improved disk clutch for a tire carrier.

SUMMARY OF THE INVENTION

The present invention provides a disk clutch for a tire carrier of amotor vehicle which overcomes at least some of the above-noted problemsof the related art. According to the present invention, a torquelimiting clutch for a spare tire carrier comprises, in combination, adrive shaft having central rotational axis and a groove, a spring membersecured to the drive shaft for rotation with the drive shaft about thecentral rotational axis, a plate adjacent the spring member androtatable about the drive shaft, and a retaining clip located within thegroove of the drive shaft and engaging the plate to retain the plate onthe drive shaft. A radial-facing abutment is located outward of theretaining clip to prevent release of the retaining clip from the groove.

According to another aspect of the present invention, a torque limitingclutch for a spare tire carrier comprises, in combination, a drive shafthaving central rotational axis and a groove, a spring member secured tothe drive shaft for rotation with the drive shaft about the centralrotational axis, a plate adjacent the spring member and rotatable aboutthe drive shaft, and a retaining clip located within the groove of thedrive shaft and engaging the plate to retain the plate on the driveshaft. The plate has a pocket forming a radial-facing abutment locatedoutward of the retaining clip to prevent release of the retaining clipfrom the groove

According to yet another aspect of the present invention, a torquelimiting clutch for a spare tire carrier comprises, in combination, adrive shaft having central rotational axis and a groove, a spring membersecured to the drive shaft for rotation with the drive shaft about thecentral rotational axis, a plate adjacent the spring member androtatable about the drive shaft, and a retaining clip located within thegroove of the drive shaft and engaging the plate to retain the plate onthe drive shaft. The plate has a pocket forming an axial-facing firstabutment engaging the retaining clip and a radial-facing second abutmentlocated outward of the retaining clip to prevent release of theretaining clip from the groove.

From the foregoing disclosure and the following more detaileddescription of various preferred embodiments it will be apparent tothose skilled in the art that the present invention provides asignificant advance in the technology and art of disk clutch assemblies.Particularly significant in this regard is the potential the inventionaffords for providing a high quality, reliable, low cost assembly.Additional features and advantages of various preferred embodiments willbe better understood in view of the detailed description provided below.

BRIEF DESCRIPTION OF THE DRAWINGS

These and further features of the present invention will be apparentwith reference to the following description and drawings, wherein:

FIG. 1 is a schematic view of a tire carrier assembly for a motorvehicle according to a preferred embodiment of the present invention;

FIG. 2 is a perspective view of a disk clutch of the tire carrierassembly of FIG. 1;

FIG. 3 is an end view of the disk clutch of FIG. 2;

FIG. 4 is an end view of the disk clutch of FIGS. 2 and 3;

FIG. 5 is a cross-sectional view of the disk clutch taken along line 5-5of FIG. 4;

FIG. 6 is an end view of a spring member of the disk clutch of FIGS. 2to 5;

FIG. 7 is a cross-sectional view of the spring member taken along line7-7 of FIG. 6;

FIG. 8 is a side view of the spring member of FIGS. 6 and 7;

FIG. 9 is an enlarged, fragmented view of a portion of the spring membertaken along line 9 of FIG. 8;

FIG. 10 is an enlarged, fragmented view of a portion of the springmember taken along line 10 of FIG. 9;

FIG. 11 is an end view of a cam plate of the disk clutch of FIGS. 2 to5;

FIG. 12 is a side view of the cam plate of FIG. 1 1;

FIG. 13 is an end view of the cam plate of FIGS. 11 and 12;

FIG. 14 is a cross-sectional view of the cam plate taken along line14-14 of FIG. 13;

FIG. 15 is an enlarged, fragmented view of a portion of the cam platetaken along line 15 of FIG. 13;

FIG. 16 is a cross-sectional view of the cam plate taken along line16-16 of FIG. 15; and

FIG. 17 is an end view of a retaining clip of the disk clutch of FIGS. 2to 5;

FIG. 18 is an enlarged, fragmented cross-sectional view showing aportion of FIG. 5 in the area of the retaining clip.

It should be understood that the appended drawings are not necessarilyto scale, presenting a somewhat simplified representation of variouspreferred features illustrative of the basic principles of theinvention. The specific design features of disk clutch for a tirecarrier as disclosed herein, including, for example, specificdimensions, orientations, locations, and shapes of the variouscomponents, will be determined in part by the particular intendedapplication and use environment. Certain features of the illustratedembodiments have been enlarged or distorted relative to others tofacilitate visualization and clear understanding. In particular, thinfeatures may be thickened, for example, for clarity or illustration. Allreferences to direction and position, unless otherwise indicated, referto the orientation of the shifter lever mechanism illustrated in thedrawings. In general, up or upward generally refers to an upwarddirection within the plane of the paper in FIG. 1 and down or downwardgenerally refers to a downward direction within the plane of the paperin FIG. 1.

DETAILED DESCRIPTION OF CERTAIN PREFERRED EMBODIMENTS

It will be apparent to those skilled in the art, that is, to those whohave knowledge or experience in this area of technology, that many usesand design variations are possible for the improved disk clutchdisclosed herein. The following detailed discussion of variousalternative and preferred embodiments will illustrate the generalprinciples of the invention with reference to a disk clutch for a tirecarrier of a motor vehicle. Other embodiments suitable for otherapplications will be apparent to those skilled in the art given thebenefit of this disclosure.

Referring now to the drawings, FIG. 1 schematically illustrates a sparetire carrier assembly 10 for a motor vehicle according to the presentinvention. The illustrated tire carrier assembly 10 includes a tirecarrier or plate 12 for carrying and supporting a spare tire 14 thereon,a winch assembly 16 for raising and lowering the tire carrier 14 betweenan upper or storing position and a lower or accessing position, arotational motion or torque input device 18 for supplying torque tooperate the winch assembly 16, and a torque limiting slip mechanism orclutch 20 operatively connecting the torque input device 18 to the winchassembly 16. The winch assembly 16 includes a rotatable lift drum orreel 22 and an elongate flexible member 24 such as a cable, rope, orcord which is wound onto and off of the lift drum 22. It is noted thatany suitable winch assembly 16 can be utilized within the scope of thepresent invention. The flexible member 24 has a first or upper endsecured to the lift drum 22 and a second or lower end connected to thetire carrier 12 so that the tire carrier 12 is raised and lowered as theflexible member 24 is wound and unwound on the lift drum 22respectively.

As best shown in FIGS. 2 to 5, the illustrated clutch 20 includes adrive shaft 26, a spring member 28, a cam plate 30, and a retaining clipor ring 32. The drive shaft 26 defines a central rotational axis 34 forthe clutch 20. The illustrated drive shaft 26 includes a first endportion 36 and a second end portion 38 which are separated by anincreased diameter or central portion 40 forming an annular-shapedabutment 42 facing the second end portion 38 for engagement by thespring member 28 as described in more detail hereinafter. Each of theillustrated first and second end portions 36, 38 and the central portion40 are substantially circular in cross-section. Adjacent the abutment42, however, the illustrated drive shaft 26 is provided with driveportion 44 that is substantially square in cross-section. The driveportion 44 is sized and shaped to cooperate with the spring member 28 tosubstantially prevent relative rotation and transmit torque therebetweenas described in more detail hereinafter. The illustrated drive shaft 26also includes a groove 46 sized and shaped for receiving the retainingclip 32. The groove 46 is located on the second end portion 38 andspaced from the abutment 42 a distance to obtain a predetermined preloadbetween the spring member 28 and the cam plate 30 as described in moredetail hereinafter.

As best shown in FIGS. 6 to 10, the illustrated spring member 28 isgenerally disk shaped having a circular-shaped outer edge 48. An opening50 is formed at the central axis 34 of the spring member 28 which issized and shaped to receive the drive shaft 26. The illustrated opening50 is substantially square shaped to cooperate with the drive portion 44of the drive shaft 26. With the drive portion 44 extending into theopening 50, a positive drive is formed between the drive shaft 26 andthe spring member 28 so that rotational motion or torque of the driveshaft 26 is transferred from the drive shaft 26 to the spring member 28.It is noted that the spring member 28 can alternatively be secured tothe drive shaft 26 in any other suitable manner. The spring member 28 ispreferably formed of steel such as, for example, C1075 CRASS butalternatively any other suitable material can be utilized.

The illustrated spring member 28 is provided with a plurality of detentsor protrusions 52 extending in an axial direction and located along theouter edge 48 of the spring member 28. The illustrated spring member 28includes four detents 52 equally spaced about the circumference of theouter edge 48, that is, spaced about 90 degrees apart. It is noted,however, that the spring member 28 can alternatively be provided withany other suitable quantity of detents 52 and can alternatively belocated at other suitable positions. The illustrated detents 52 are inthe form of bosses formed at the outer edge 48 of the spring member 28.Located at the outer edge 48 assures forming to be more accurate andconsistent. The illustrated bosses 52 are formed at the outer edge 48and extend in the radial direction so that an inner end 54 of the boss52 is closed while an outer end 54 of the boss 52 is open (best seen inFIG. 10). The illustrated bosses 52 form an engagement surface 58 whichis generally V-shaped in cross section. The angle A formed by theengagement surfaces 58 of the bosses 52 is preferably greater than 90degrees and more preferably about 96 degrees.

As best shown in FIGS. 11 to 16, the illustrated cam plate 30 isgenerally disk shaped having a circular-shaped outer edge 60. The outeredge 60 is also provided with an axially extending flange 62 to form acavity 64 for receiving the spring member 28. An opening or passage 66is formed at the central axis 34 of the cam plate 30 which is sized andshaped to receive the drive shaft 26. The illustrated opening 66 issubstantially circular-shaped to cooperate with the second end portion38 of the drive shaft 26. With the second end portion 38 extending intothe opening 66, the drive shaft 26 is rotatable relative to the camplate 30. Formed in the end face of the drive shaft 26 about the opening66 is a pocket 67 sized and shaped for receiving the retaining clip 32as described in more detail hereinafter. The illustrated pocket 67 is acircular-shaped counter bore but any other suitable shape canalternatively be utilized. The illustrated pocket 67 forms an axiallyfacing annular 67 a shaped first abutment for engagement by theretaining ring 32 as described in more detail hereinafter and a radiallyinward facing cylindrically shaped second abutment 67 b for preventingundesirable release of the retaining clip 32 from the shaft 26 asdescribed in more detail hereinafter. The illustrated second abutment 32b forms a continuous surface encircling the central axis 34.

The illustrated cam plate 30 also includes an eccentric cam 68 providedabout the central axis 34 opposite the cavity 64 and a plurality of camsurfaces or notches 70 equally spaced about the circumference of theouter edge 60. The eccentric cam 68 and the plurality of cam notches 70are each sized and shaped to cooperate with the lift drum 22 to transmitrotary motion or torque of the cam plate 30 to the drive drum 22. Thecam plate 30 is preferably formed of powder metal but alternatively anyother suitable material can be utilized.

The illustrated cam plate 30 is provided with a plurality of grooves orpockets 72 within the cavity 64 and located near the outer edge 60 ofthe cam plate 30. The grooves 72 are positioned, sized and shaped toreceive and cooperate with the detents 52 of the spring member 28. Theillustrated cam plate 30 includes 8 grooves equally spaced about thecircumference of the outer edge 60, that is, spaced about 45 degreesapart. It is noted, however, that the cam plate 30 can alternatively beprovided with any other suitable quantity of the grooves 72 and thegrooves 72 can alternatively be located at other suitable positions. Itis noted that the illustrated cam plate 30 is provided with a greaterquantity of the grooves 72 than the quantity of the detents 52 of thespring plate 28 to reduce the amount of rotation required by the springmember 28 to reengage the detents 52 with the grooves 72 upondisengagement. The illustrated grooves 72 are formed radially inward ofthe flange 62 and do not extend through the entire thickness of the camplate 30 so that they are entirely closed except for a single open side(best seen in FIG. 15) through which the detents 52 enter. It is notedthat alternatively other shapes and locations can be utilized such as,for example, the grooves 72 can be open at their bottoms or out ends.The illustrated grooves 72 form an engagement surface 74 which isgenerally V-shaped in cross section to cooperate with the engagementsurfaces 58 of the detents 52. The angle B formed by the engagementsurfaces 74 of the grooves 72 is preferably greater than 90 degrees andmore preferably about 96 degrees.

As best shown in FIG. 17, the illustrated retaining clip 32 is an E-ringthat is an American Standard metric reduced cross section retaining ringexternal series #CM1-12. The retaining clip 32 can alternatively haveany other suitable size and shape. The retaining clip 32 is sized andshaped to cooperate with the groove 46 of the drive shaft 26 to providean axially-facing abutment for engagement with the first abutment 67 aof the cam plate pocket 67 to rotatably secure the cam plate 30 onto thedrive shaft 26.

As best shown in FIG. 18, the first abutment 67 a of the cam platepocket 67 engages the retaining clip 32 in the axial direction to retainthe cam plate 30 on the drive shaft 26. The second abutment 67 b of thecam plate pocket 67 encircles the retaining clip 32. With the secondabutment encircling the retaining clip 32, the retaining clip 32 cannotbe released from the drive shaft 26 because the retaining clip engagesthe second abutment 67 b to prevent further movement. The pocket 67 ispreferably sized so that the retaining clip 32 does not substantiallyengage the second abutment during normal operation of the clutch 20, butprovides positive retention of the retaining clip 32 to the drive shaft26.

As best shown in FIGS. 2 to 5, the clutch 20 is assembled by insertingthe second end portion 38 of the drive shaft 26 into the spring memberopening 50 until the spring member 28 engages the abutment 42 and thedrive portion 44 of the drive shaft 26 is located within the springmember opening 50. Located in this manner, the spring member 28 isrigidly secured to the drive shaft 26 for rotation therewith. The secondend portion 38 of the drive shaft 26 is then inserted into the cam plateopening 66 until the cam plate 30 engages the spring member 28 with thespring member detents 52 located within the cam plate grooves 72. Thecam plate 30 is then further moved along the drive shaft 26 bycompressing the spring member 28 until the drive shaft groove 46 isexposed. With the groove 46 exposed, the retaining clip 32 is insertedinto the drive shaft groove 46 and the cam plate 30 is released so thatthe spring member 28 axially moves the cam plate into engagement withthe retaining clip 32 to retain the cam plate 30 in a desired engagementwith the spring member 28. In this position, the retaining clip 32 islocated within the pocket 67 of the cam plate 30. When assembled in thismanner, rotation of the spring member 28 causes rotation of the camplate 30 below a predetermined torque limit as the detents 52 engage thegrooves 72 to rotate the cam plate 30 with the spring member 28 and thedrive shaft 26. However, above the predetermined torque limit, thedetents 52 resiliently deflect out of engagement with the grooves 72 sothat the spring member 28 rotates with the drive shaft 26 withoutrotating the cam plate 30. The retaining clip 32 cannot “pop off” or beinadvertently released from the drive shaft 26 because its movement islimited by the second abutment 67 b of the cam plate pocket 67.

The drive shaft groove 46 can be relocated to different positions toobtain a different pretension on the spring member 28. The pretensionsallow different torque trips, that is, torque limits. The illustrateddetents and grooves 52, 72 allow for a wide range of working motion andpretension. This range can be, for example, from a free/loose springmember 28 to a spring member 28 with about 0.20 mm of pretension. Itshould also be appreciated that different torque trips can be achievedwith the same spring member and cam plate 28, 30. This results in theability to tightly control the torque and tension of all tire carrierassemblies 10 to their intended performance specification ranges whileusing common components.

The clutch 20 is assembled into the tire carrier assembly 10 by operablyconnecting the eccentric cam 68 and the plurality of cam surfaces 70 ofthe cam plate 30 to the lift drum 22 so that rotational motion or torqueof the cam plate 30 is transferred to the lift drum 22 to rotate thelift drum 22. The drive shaft 26 is operatively connected to a torqueinput device 18 so that rotational motion or torque of the torque inputdevice 18 is selectively transferred to the drive shaft 26 to rotate thedrive shaft 26 and the spring member 28. The torque input device 18 canbe either a manual device such as, for example, a handle or toolattachment so that a user can manually rotate the drive shaft 26 or apowered device such as, for example, an electric motor that selectivelyrotates the drive shaft 26.

In operation, when the tire carrier 12 is in its lower position androtational motion or torque is applied by the torque input device 18 torotate the drive shaft 26, the drive shaft 26 rotates the spring member28 which in turn rotates the cam plate 30 through the engagement of thedetents 52 with the grooves 72. The rotation of the cam plate 30 in turnrotates the lift drum 22 to wind the cable 24 onto the lift drum 22 andlift the tire carrier 12 with the spare tire 14 thereon. When the tirecarrier 12 reaches its upper position and tension in the cable 24increases so that the predetermined torque limit of the clutch 20 isreached, the detents 52 of the spring member 278 resiliently deflect outof engagement with the grooves 72 of the cam plate 30 so that torque isnot transmitted from the spring member 28 to the cam plate 30. Thus, thecam plate 30 and the lift drum 22 stop rotating even though rotation ofthe drive shaft 26 and the spring member 28 may continue to avoidundesirable tension in the cable 24.

It is apparent from the above detailed description of the presentinvention, that the illustrated clutch 20 provides positive retention ofthe retaining clip 32. This avoids failure of the clutch 20 due toinadvertent release of the spring clip 32 from the drive shaft.

From the foregoing disclosure and detailed description of certainpreferred embodiments, it is also apparent that various modifications,additions and other alternative embodiments are possible withoutdeparting from the true scope and spirit of the present invention. Theembodiments discussed were chosen and described to provide the bestillustration of the principles of the present invention and itspractical application to thereby enable one of ordinary skill in the artto utilize the invention in various embodiments and with variousmodifications as are suited to the particular use contemplated. All suchmodifications and variations are within the scope of the presentinvention as determined by the appended claims when interpreted inaccordance with the benefit to which they are fairly, legally, andequitably entitled.

1. A torque limiting clutch for a spare tire carrier comprising, incombination: a drive shaft having central rotational axis and a groove;a spring member secured to the drive shaft for rotation with the driveshaft about the central rotational axis; a plate adjacent the springmember and rotatable about the drive shaft; a retaining clip locatedwithin the groove of the drive shaft and engaging the plate to retainthe plate on the drive shaft; and a radial-facing abutment locatedoutward of the retaining clip to prevent release of the retaining clipfrom the groove.
 2. The torque limiting clutch according to claim 1,wherein the abutment is formed by a pocket in the plate.
 3. The torquelimiting clutch according to claim 2, wherein the pocket is formed by acounter bore in the plate.
 4. The torque limiting clutch according toclaim 3, wherein the counter bore is circular.
 5. The torque limitingclutch according to claim 2, wherein the pocket is circular.
 6. Thetorque limiting clutch according to claim 2, wherein the pocket alsoforms an axial-facing abutment engaging the retaining clip.
 7. Thetorque limiting clutch according to claim 1, wherein the abutment iscylindrically-shaped.
 8. The torque limiting clutch according to claim1, wherein the abutment encircles the retaining clip
 9. The torquelimiting clutch according to claim 8, wherein the abutment is continuousabout the retaining clip.
 10. The torque limiting clutch according toclaim 1, wherein the retaining clip is an E-ring.
 11. A torque limitingclutch for a spare tire carrier comprising, in combination: a driveshaft having central rotational axis and a groove; a spring membersecured to the drive shaft for rotation with the drive shaft about thecentral rotational axis; a plate adjacent the spring member androtatable about the drive shaft; a retaining clip located within thegroove of the drive shaft and engaging the plate to retain the plate onthe drive shaft; and wherein the plate has a pocket forming aradial-facing abutment located outward of the retaining clip to preventrelease of the retaining clip from the groove.
 12. The torque limitingclutch according to claim 11, wherein the pocket is formed by a counterbore.
 13. The torque limiting clutch according to claim 12, wherein thecounter bore is circular.
 14. The torque limiting clutch according toclaim 11, wherein the pocket is circular.
 15. The torque limiting clutchaccording to claim 11, wherein the abutment is cylindrically-shaped. 16.The torque limiting clutch according to claim 11, wherein the abutmentencircles the retaining clip
 17. The torque limiting clutch according toclaim 16, wherein the abutment is continuous about the retaining clip.18. The torque limiting clutch according to claim 11, wherein the pocketforms an axial-facing abutment engaging the retaining clip.
 19. Thetorque limiting clutch according to claim 11, wherein the retaining clipis an E-ring.